I seem to recall this being fairly easy to trigger by simply pulling
the network cable while there's heavy mmap + write load. The system
will quickly spiral down into OOM and will remain wedged when you plug
the network back in. With iSCSI, after some extended period all the
I/Os will have SCSI timeouts and lose everything.

This has actually been brought up when the scsi_times_out thread was going
on. It kinda was at least. Some driver writers inluding sfnet used to play
a lot of tricks with the timers to accomplish this (this was the goal
for sfnet at least) and I do not think linux-scsi will allow it. Maybe that
will change.
host block/unblock logic in recent iSCSI transport

patch will help to implement that.

No it won't :( block/unblock does not disable timeouts it just makes it
so new commands are not queued and they timeout when the driver knows
that the transport is hosed.